Fluid distribution doors in vehicle climate control or heating, ventilating, and fluid conditioning (HVAC) systems distribute a fluid through the vehicle according to passenger settings. Varying pressures within the HVAC system can cause unsteady forces which impede fluid distribution and lead to vortex shedding, door vibration or flutter, which ultimately leads to noise resonating throughout the HVAC system. Typically, the HVAC systems are generally closed systems, which amplify noise produced therewithin. Vortex shedding is defined as an unsteady flow of fluid that is caused by fluid movement past a blunt or bluff object (e.g. the fluid distribution door). The flow of the fluid past the fluid distribution door can produce alternating low pressure vortices. When this occurs, the fluid distribution door tends to move toward a zone of lower pressure, which causes the fluid distribution door to vibrate and flutter.
Typically, the fluid distribution door is a relatively large hinged-free type plate, and can be characterized as a two-dimensional bluff body in aerodynamics. In fluid flow passages of an HVAC module, the fluid distribution door is a bluff body which produces vortex shedding or wakes as fluid flows over exposed surfaces of the fluid distribution door, especially at peak fluid flow and pressure conditions. The vortex shedding and wakes can generate large unsteady forces, even intense vibrations, which have the potential to violently move or damage the structural integrity of the fluid distribution door. For this reason, effects of the vortex shedding need to be controlled to decrease an amplitude of fluctuating lift, as well as drag on the fluid distribution door.
Furthermore, the fluid distribution door should be stiff enough to transfer torque without bending or breaking. If the fluid distribution door bends too much, it provides inadequate sealing and may exhibit creep when the stress and strain approaches or exceeds a yield strength thereof. To prevent bending, prior art fluid distribution doors include additional features such as ribs or other two-dimensional features. However, these features usually increase a weight and a size of the fluid distribution door, as well as cause dimensional instability during a manufacturing, including, for example, warping.
Accordingly, it would be desirable to produce a fluid distribution door for an HVAC system that maximizes performance, efficiency, and structural integrity, while minimizing a cost and a complexity thereof.